Are you dealing with a pesky check engine light in your pre-1996 4.3L V6 Chevrolet S10 pickup (GMC S15 pickup, GMC Sonoma)? It can seem like a daunting task to retrieve the diagnostic trouble codes, but don't worry - this tutorial will help!
In this guide, I'll cover how to use the on-board diagnostic (OBD) system to display the trouble codes stored in the fuel injection computer and which diagnostic link connector (DLC) terminals need to be jumpered in order to retrieve the diagnostic trouble codes (DTCs).
Keep reading for all the details you need to get your Chevy S10 pickup (GMC S15 pickup, GMC Sonoma) back on the road!
Contents of this tutorial:
Reading The On/Off Flashes Of The Check Engine Light
The diagnostic link connector (DLC), also known as the Assembly Line Data Link (ALDL) connector, is located under the dash, usually on the right side of the steering wheel column.
This connector is the same across all pre-OBD II GM vehicles. You can see what the ALDL connector looks like in the photo at the beginning of this tutorial.
In order to retrieve the diagnostic trouble codes stored in the memory of the fuel injection computer, you'll need "jumper" two terminals together. You can use a paper clip or a small piece of wire with both ends stripped.
These are the steps to retrieve the trouble codes:
- Make sure your battery is fully charged before starting (its customary to place a charger on the battery while retrieving trouble codes to keep the battery from discharging).
- Turn the key to the ON position but don't start the vehicle.
- Jumper terminals A and B, of the diagnostic link connector, together.
- If no trouble codes are present:
- The MIL will flash a code 12 (see illustration below) which consists of one flash, a short pause, then two flashes in rapid succession. Code 12 would look like this:
- ‘Flash’, pause, ‘flash’, ‘flash’, long pause.
- Code 12 will is repeated another 2 times (all codes are flashed 3 times before the next one).
- The MIL will flash a code 12 (see illustration below) which consists of one flash, a short pause, then two flashes in rapid succession. Code 12 would look like this:
- If trouble codes are present:
- The MIL will flash code 12 three times and then any other codes stored.
- Each trouble code, in addition to code 12, is flashed 3 times.
- A code 22 would look like this:
- ‘Flash’, ‘flash’, pause, ‘flash’, ‘flash’, long pause.
Once you've confirmed and written down the trouble codes, remove the jumper wire from the diagnostic link connector (DLC) and turn the key to the Off position.
GM OBD I Diagnostic Trouble Code Definitions
| Chevy S10/GMC S15 OBD I Trouble Code Definitions | |
|---|---|
| Code | Description |
| 12 | System Check |
| 13 | Oxygen Sensor Circuit |
| 14 | Engine Coolant Temperature (ECT) High Temperature Indicated |
| 15 | Engine Coolant Temperature (ECT) Sensor Signal Voltage High |
| 16 | Transmission Speed Error |
| 21 | TPS Signal Voltage High |
| 22 | TPS Signal Voltage Low |
| 23 | MAT (Manifold Air Temperature) Signal Voltage High |
| 24 | Vehicle Speed Sensor (VSS) Signal Voltage High |
| 25 | MAT (Manifold Air Temperature) Signal Voltage Low |
| 26 | Quad Driver 1 Fault (4.3L M/T only) |
| 27 | Quad Driver 2 Fault (4.3L M/T only) |
| 28 | Transmission Pressure Switch Manifold Range Circuit Problem |
| 32 | EGR System Failure |
| 33 | MAP Sensor Signal Voltage High |
| 34 | MAP Sensor Signal Voltage Low |
| 35 | Idle Speed Error |
| 37 | Brake Switch Stuck On (4L60-E A/T only) |
| 39 | Knock Sensor Circuit Shorted (4.3L M/T Only) |
| 42 | Electronic Spark Timing (EST) Fault |
| 43 | Electronic Spark Control (ESC) Fault |
| 44 | Lean Exhaust |
| 45 | Rich Exhaust |
| 51 | PROM/MEM-CAL Fault |
| 51 | System Voltage High (Charging System Problem) |
| 54 | Fuel Pump Circuit |
| 54 | Faulty ECM/PCM/VCM |
More 4.3L Chevy S10 Pickup, GMC S15 Pickup, And GMC Sonoma Tutorials
You can find a complete list of 4.3L Chevy S10 pickup, GMC S15 pickup, And GMC Sonoma tutorials here:
Here's a sample of the tutorials you'll find in the index:
- How To Test The Fuel Pump (1996-2003 4.3L V6 Chevrolet S10 Pickup, GMC Sonoma).
- How To Test The EGR Valve (1988-1995 4.3L TBI Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma).
- How To Test For A Blown Head Gasket (1988-2003 4.3L Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma).
- How To Test Engine Compression (1988-2003 4.3L V6 Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma).
If this info saved the day, buy me a beer!
